Natural weathering study of the resistance of various glass types against UV-induced color fading

 

The fading effect of UV radiation on color pigments is widely known, the most common is the loose of color intensity in clothes. A high UV-resistance of window and façade glazing is urgent for the conservation and preservation of historical exhibits and interiors.

In this contribution, a long-lasting natural weather testing of several glass types, mostly LSG with different interlayer materials, and the effect of the different color patterns of paper and textile specimens are presented. According to the Harrison damage function, the initial damage level starts at 500 nm wavelength. Therefore, besides standard PVB-interlayer (UV-blocking from 360 nm wavelength) also special UV-blocking interlayer (UV-blocking from 400 nm) are part of the study. The research was conducted over the entire summer of 2022.

The assessment of the bleaching effect was measured as color difference according to the CIELAB color space and verified by human eye perception. The CIELAB color space is the most used color system and combines brightness, yellow-blue and red-green tones.

The research shows a significant effect of different glass build-ups on the color difference value, especially for medium-sensitive pigment papers and textiles. Furthermore, the color shifting of single color test strips showed demonstrated the limitation of the color difference value of the CIELAB color space versus the human eye perception.

 

 

 

Numerical simulation of impact on glass panes and the fracture energy equilibrium

 

The Griffith theory describes the behaviour of brittle materials. For the description of a crack creation, an energy equilibrium is used. At annealed glasses, this equilibrium is reduced to a simple formula containing the mechanical energy in the glass and the surface energy needed for crack creation. However, this theory is developed for low-velocity static testing. In this paper, this theory is applied to a ball drop test which involves high-velocity crack propagation. Although the measured surface energy coefficient was constant, it was significantly higher than to statically determined coefficient. This was explained by the partial use of the potential energy of the ball drop for the crack creation. A numerical model is developed and compared to explain this partial use of potential energy.